FP, would at least send a clear signal of what is socially acceptable, which often changes social norms along the way (though not always).
Laws with inherently vague standards attached to them are not good ways to send a clear signal.
The standards aren't vague. Any woman can tell the difference between actual compliments and harassment.
Even acknowledging a woman's infallible capacity for categorization of communications, can a man also tell this difference?
Even if he can't tell the difference on his own, he could ask a woman what is OK and what isn't.